Reference array with char?

Using Arduino Programming Questions
#1

I’m having a problem that might not be too common. I have several arrays and I want to reference each array with a char. However, I get the error message “invalid types ‘char[int]’ for array subscript”.

int a[] = {0, 1};
int b[] = {1, 2};
char letter = 'a';

void setup() {
  Serial.begin(9600);
}


void loop() {
  Serial.print(letter[1]);
}

stranger_things_backup.ino (140 Bytes)

#2

(deleted)

#3

Looks like the OP thinks having “letter” set to ‘a’ will access elements in array “a”.
Having letter set to ‘b’ will access elements in array “b”.

C/C++ is a compiled language. You can not access/modify variable names at runtime.

int a[] = {0, 1};
int b[] = {1, 2};
int* arrays [] = { a, b };

char letter = 'a';
if (letter >= 'a' && letter <= 'b')
{
   Serial.print(arrays[letter-'a'][1]);
}

Edit: Note the above ONLY works because the array names as sequential and consecutive letters (because of letter-‘a’).
Also, if all the arrays are the same length, you might do better with a 2 dimensional array.

#4

pcbbc:
Looks like the OP thinks having “letter” set to ‘a’ will access elements in array “a”.
Having letter set to ‘b’ will access elements in array “b”.

C/C++ is a compiled language. You can not access/modify variable names at runtime.

int a[] = {0, 1};

int b = {1, 2};
int* arrays = { a, b };

char letter = ‘a’;
if (letter >= ‘a’ && letter <= ‘b’)
{
  Serial.print(arrays[letter-‘a’][1]);
}



Edit: Note the above ONLY works because the array names as sequential and consecutive letters (because of letter-'a').
Also, if all the arrays are the same length, you might do better with a 2 dimensional array.

You are right, that was what I hoped to achieve. However, as you have pointed out it doesn’t seem to be allowed in the C language. I tried your suggestion but ended up circumventing my problem with a switch case. Thank you for your suggestion!

#5

seems awkward

results

func: 0 [0]  0
func: 0 [1]  1
func: 1 [0]  2
func: 1 [1]  3
func: 0 [2]  2
func: 0 [3]  3
func: 0 [4]  0

#include <stdio.h>

int arr [2][2] = {
    { 0, 1 },
    { 2, 3 },
};

void
func (char c, int i)  {
    printf ("%s: %c [%d]  %d\n", __func__, c, i, arr [c - '0'][i]);
}

int
main ()
{
    func ('0', 0);
    func ('0', 1);
    func ('1', 0);
    func ('1', 1);

    func ('0', 2);
    func ('0', 3);
    func ('0', 4);
}
#6